A Basis of Understanding
by Tentaspy
Summary: Mordekaiser and Karthus find that they're much closer than originally imagined. (I wanted to write Mordekaiser/Karthus, so I did. Karthus is transgender, don't like don't read. I will not tolerate transphobic comments in the reviews. This fic may be added to at a later date.)


Karthus had a voice like no other. Though he had a specific voice for his role in Pentakill, he could literally copy or produce any kind of voice he desired. One of the many perks of being dead, he would enforce. Today, much like any other rainy day, he was singing opera. A one man duet, solemn and without instruments, it sounded as if the Shadow Isles themselves were in chorus. Beneath the balcony he stands on, the dead stirs to life, the bones and flesh of once rotten corpses renewed. His voice was what sustained them, and controlled them, their mindless movements as fluid and graceful as his song.

His song comes to a rather abrupt end, his control on the creatures below fading quickly. They all fall over in unison, their flesh returning to the ground and their bones resuming their decay into dust.

He turns around to find Mordekaiser standing behind him, his enormous form nearly taking up the entire doorway. "Can I help you?" He hisses, his eyes narrowing. Karthus didn't much like being interrupted.

"Sona is livid with me and she refuses to share a room with me." He says bluntly.

"So then find another room, there's plenty more." The five of them lived in an enormous magical mansion, placed deep within the Shadow Isles. There had to be at least a hundred or so rooms in the building, each with its own unique decor and furnishings.

"You know I can't just do that." Mordekaiser was much too large to fit through most of the doorways. His room had been modified to fit his size. The room itself was previously two rooms, but they knocked down one of the walls to combine them. The doorways extended all the way to the ceiling, and most of the room was left as open space so he would have room to move about. He had his own bed, as well, which was much larger than any other in the house.

However, his wasn't the only room like it. Karthus was a fickle fellow, he required the best, and only the best. His room was edited apon arrival as well. Bookcases lined the walls from ceiling to floor, covering every inch of wall space that wasn't a door or window. Though his doorways were smaller, his room was nearly identical to Mordekaiser's in size, including his bed. It was obvious what Mordekaiser was implying.

"You can't borrow my room." Karthus immediately says, refusing to even consider it.

"Then what do you want me to do? I can't go knocking down walls without help from Olaf, I'll turn this building into dust." The last time Mordekaiser tried to "fix" something, he ended up nearly collapsing his side of the house. Olaf was much more precise with his bludgeoning, and also not ten feet tall and weighing nearly five hundred pounds.

"Console your girlfriend. Make up."

"I've tried that. She says she just needs her space." Despite being a harbinger of pain and destruction, he was a huge pushover when it came to his girlfriend. Whatever she said was his rule.

Karthus ponders for a moment, "What's in it for me?"

"Fuck if I know. What do you want?"

"If I had to choose, it would be for you to stop interrupting my sessions."

"Done."

"No, no, I require more." He glances off again, pondering. "But alas, I am at a loss. Perhaps you'll just have to wait."

"Whatever I am able to do, I will." Sleeping out in the yard was the last thing he wanted to do, specifically because there was simply no sleep involved. The creatures, although not dangerous to them, were a constant bother. Yorick had to deal with them on a daily basis, and he chose to, but only because his patience equated to that of a brick wall. That, and because he could sleep through just about anything.

"Mhm, good. Then you shall be in my debt."

"So you'll let me?"

"Yes, but only for the night. And you are not permitted to touch any of my books, or my artifacts, or my-"

"Yes, yes. I won't touch anything."

"Do NOT interrupt me." Karthus scolds, his eyes glowing brighter. "You are already pushing my limits by shortening my sessions."

Mordekaiser rolls his eyes, "Apologies."

"Also, please leave your filthy armor at the door. And please clean yourself thoughly before entering my space." Mordekaiser wasn't lacking personal hygiene in any sense, but Karthus was known to be a bit of a perfectionist.

"Understood."

Not a minute late of sunset, Mordekaiser appeared at his ally's door, pristine and unclothed save for the clothes he planned to sleep in, which included a pair of oversized pants with a repeating skull and crossbones pattern on them.

Opening the door, Karthus glances over Morde briefly before letting him in. "Now, you are allowed nine hours of rest before you must leave. That nine hours starts in exactly fifteen minutes." He closes the door behind them, levitating over to the side of the bed. "You must stay within six feet of me at all times-"

"Wait, we're sharing the bed?"

Karthus twitches with rage. "What did I tell you about interrupting me?"

Mordekaiser sighs, "Right, sorry."

The Deathsinger exhales deeply, "Moving on." He floats over to the other side of the enormous bed, removing his mantle and robe and dressing himself in his nightclothes. "Did you actually think I was just going to leave you alone in MY room for the night? Heavens no. Knowing you, my room would be in small, sticky pieces by the time the sun came up."

"Uhh... right, yeah." Morde didn't exactly know how Karthus expected him to do that, considering all he was going to do was rest, but he decided not to ask questions.

"So I'll be supervising you while you visit." He sits on the side of the bed, the book he was previously reading drifting off back into its place on the bookshelf. "Mm, I hope you don't snore. I might just have to cut your throat." He looks over to the other once more, giving him a sarcastic smile. "Well? Come. Lights are going out in five."

Mordekaiser obeys immediately, climbing into bed and making himself comfortable beneath the sheets. His form took up nearly half of the bed, but there was plenty of room for Karthus' tiny form to fit comfortably with several feet to spare. The deathsinger's estimate of six feet was just about right, which made the guitarist wonder if he'd actually measured it out beforehand, because that was just like him.

Exactly five minutes later, the torches around the room collectively extinguish, leaving the room completely dark save for the moonlight coming through the balcony window.

Karthus was mildly annoyed by Mordekaiser's breathing. It was something he hadn't actually thought about, the fact that Morde was still technically alive. Karthus would be too, if it wasn't for Mordekaiser's damn guitar being cursed. Not that he minded being dead, especially considering what wonderful new abilities it came with.

His thoughts are interrupted as Mordekaiser shifts position, moving closer. Karthus couldn't see him, as he was laying on his side facing away from him, but he could feel the air shift between them. He ignores it, and starts to drift off.

His eyes fly open as Mordekaiser's huge hand lands on his hip. At first he assumes that the brute had just rolled over, but that assumption flies out the window as Morde begins to drag him closer, his fingers dipping lower.

"W-What do you think you are doing?" He hisses, trying to writhe out of Mordekaiser's strong grip. His back meets with the other's chest and he shivers at the warmth of his body.

Mordekaiser says nothing, pushing aside Karthus' robe and slipping his fingers between the singer's legs, earning a startled cry from him.

"W-What the fuck are you-" His sentence is cut short as Morde rubs him roughly. "F-Fuck off..."

"Shut up." Mordekaiser commands, "I know this is what you want."

The Deathsinger's mind briefly drifts off to the time when they were trying to recruit Olaf. Yorick and Olaf were arm wrestling, and it was tied. They had been there for almost an hour, and Sona had already gotten into the rest of the bar's alcohol. They were all pretty drunk, save for Karthus, who was dead, and therefore wasn't affected by the stuff. Him and Mordekaiser had left the room for a moment, and Morde had asked him to help him with something. Of course he followed, and then found himself cornered. Mordekaiser kissed him, and he kissed back, and damn if it didn't feel good, and damn if he wasn't trying to go further before Sona came in...

Karthus bites his lip as the other shifts behind him, pressing his body closer. Those damned fingers kept teasing him, but not going further. No, he didn't want them to go further... This wasn't happening. He squirms some more, but his tiny form poses no opposition to Mordekaiser's wall of flesh.

"You can always say no." He wasn't about to violate his ally's personal comfort to the extent of actually raping him, oh no. Despite his normally bloodthirsty and deadly intentions, he wasn't the type to do that. "But I don't think you will."

Karthus lets out a stifled moan in place of words, his body beginning to relax. He didn't want to admit defeat, but be damned if he didn't want this. The thoughts that ran through his mind were... nothing but naughty.

"Well? Make up your mind, Deathsinger."

Karthus mumbles something under his breath, biting his lip.

"Can't hear you." Morde laughs a little, the tip of his finger running over Karthus' clit softly.

"I... do not refuse..."

"Hmph, didn't think so." He finally presses his finger inside, earning another moan from the Deathsinger, his body tensing up. "So predictable."

"S-Shut up..." Karthus wraps his fingers around Morde's hand, pushing it deeper impatiently. Morde complies, his fingers slick with fluid as he plunges them deeper, aiming for that little bundle of nerves that he knows will make Karthus sing.

Morde leans in and plants a kiss on the Deathsinger's neck, his warm breath cascading down the other's lifeless flesh. "Mmh, right here..."

As he hits the spot, Karthus' body spasms, his back arching. "A-Ah, my god..." His voice was much higher pitched than before, not to mention breathy and stuttered. How he had found that spot so easily, Karthus would never know.

Morde smiles devilishly, feeling his own arousal coming to life. He swiftly strips off his trousers, pressing his erection closer and relishing the feeling.

Karthus bites his lip, reaching back and stroking the length of Morde's cock gently, fingertips running over the ladder of piercings on the underside of it. He'd forgotten how large Morde was, and that wasn't just referring to the size of his body. His mind had never been so overcome with lewd thoughts before.

The master of metal continues to rub that delicate bundle of nerves until Karthus cries out in bliss, his muscles tensing up once more before hitting climax. Mordekaiser withdraws his fingers, laying another kiss on the vocalist's cheek before forcing him onto his front.

"W-What are you..." Still lost in the wave of his orgasm, Karthus' words are barely understandable. He complies with the repositioning, stretching his arms out in front of him and spreading his legs.

"Hush." Morde grabs the other's thighs, positioning himself between them. He teases Karthus' dripping entrance with the tip of his cock, his grin returning as his victim squirms beneath him.

"Nngh, fuck..." Karthus normally wasn't one to curse as much as the others, but it was obvious that this was a special occasion. "S-Stop teasing..."

"I said, shut up." With one hand Morde grabs the singer's neck, gripping it tightly. "I'll tell you when you can speak." For him, it felt wonderful to actually be in control. With Sona, he was always extra careful not to hurt her, but since Karthus was already dead...

With his free hand, Morde guides his cock into place, pushing it inside slowly. He bites his lip as his throbbing cock is engulfed completely. This too, was different from his girlfriend. Sona's small pussy couldn't even begin to accomodate the entirety Mordekaiser's huge organ, and the change of pace was damn near enlightening. Not to mention the differences between their flesh, one being warm and the other rather cold. The sensation wasn't unpleasant, however.

He pulls his cock out, pushing it back in a moment after. Oh yes, this truly was enlightening. The feeling of being completely enveloped nearly brought him to climax immediately, but he paused and managed to suppress it. Mordekaiser was well known for his... urges. Sexual or not. There were some times when even Sona couldn't sate his endless lust. Why hadn't they done this before?

Morde's hand drifts away from the singer's neck, resting on the pillow beneath him for leverage. Karthus didn't much like being silenced. Taking the opportunity, he bites down on Morde's hand, hand enough to draw a bold line of blood. Morde reacts immediately, grabbing Karthus' neck and pulling him upright. "You bitch!"

Karthus manages to stifle a laugh, licking his lips clean of the other's blood with a smile.

Mordekaiser hisses back, forcing the Deathsinger's face back into the bed and placing his hand on the back of his head. The brute pulls his cock out, only to slam it back in afterwards, earning a moan from the other. "Fine then, sing for me." His rhythm starts off slow, but it quickly escalates into something vicious, each thrust as strong and forceful as the last. Karthus couldn't help himself, he was in chorus.

"Mmh, perfect." Mordekaiser loved hearing the other moan beneath him. Although he certainly wouldn't admit it to his girlfriend, he loved it when his partners were vocal.

Finally finding climax, he leans in, pulling Karthus into a brief kiss, tasting his own blood still lingering on the other's lips.

"If you want to kiss me... you should fuck me from the front." Karthus was exhausted, but he wasn't done yet. This was too perfect to let it end so soon.

"Oh? Giving in so easily?" Mordekaiser laughs, removing himself and letting Karthus turn himself over. The singer gazes up at him with hungry eyes, spreading his legs again eagerly. "You're such a whore."

"Shut up and fuck me already." The Deathsinger orders, arching his back and resting his legs on Morde's hips.

"So impatient." Morde wraps his fingers around the other's thighs tightly, pulling him close and pressing his cock closer. "You can't always get what you want, you know."

"Fuck you." Karthus hisses back, glaring at Morde with blazing eyes. He couldn't exactly come up with any witty responses at the moment, so a death stare would have to suffice.

"My, my, so vulgar. What's gotten into you?" Morde laughs, pulling Karthus forward and entering him swiftly, a keen howl escaping his victim's lips. "Oh... right. Heh heh." His hands move to grasp Karthus' bony hips, his palms fitting nicely over the bulges of his bone structure. Using this leverage he begins his rhythm, bouncing the other on his cock as if he were a mere toy.

Though taking him from behind was a play on control, Morde loved actually seeing Karthus squirm beneath him. Watching him sing was already enjoyable, but being the curator of his melody was even sweeter.

Morde leans over him, his thrusts becoming rougher. "Can you hear yourself? You're such a slut..." He captures Karthus' lips in a rough kiss, drawing blood across the singer's bottom lip. He would retaliate, of course, biting back and enjoying the metallic taste that fills his mouth. Oh, how he loved the taste of fresh blood. Likewise, Mordekaiser loved it when they fought back.

"You'll regret that." The brute growls, pulling back and wiping his chin clean of blood.

"You know that I have no regrets." Karthus responds, laughing again.

"I'm sure you'll reconsider in the morning when your body is beaten and bruised." Morde grabs the singer's throat once again, digging his nails into his tender flesh. He continues pounding at Karthus' entrance until finding release once more, riding out his orgasm and then collapsing at the singer's side.

The two take a moment to gather their breath before returning to their sleeping positions.

"You will not speak of this. To anyone." Karthus says sternly.

"Wasn't planning on it. I am in a relationship, you know."

"Good."

The silence returned, and Karthus felt himself drifting off into sleep. However, just before his mind stilled, he felt a strong arm wrap around his waist once more. Turning his head, he scowls at the guitarist. "What?"

Morde pulls Karthus' tiny form closer to his own, planting a brief kiss on his forehead. "Don't pretend like we didn't just do that. Sleep next to me."

Karthus rolls his eyes, "I'm not pretending anything, you oaf." He gives in, snuggling up next to Morde, laying his head on the guitarist's huge bicep and draping his arm across his wide chest. "Now go to sleep. You've already wasted an hour of my precious time."

"Pfft, wasted? You wish." Morde smiles, rubbing Karthus' hip with his thumb. "I haven't heard you sing that loud since Freljord."

"Shut up." Karthus says as he nuzzles the other's chest, shutting his eyes.

Sleep comes quickly for the both of them, lewd images swimming behind their eyelids until the light of day rouses them from oblivion. Exhaustion had surely overtaken them, as they were in the exact same position they'd laid down in.

Karthus was the first one to awaken. Taking a quick look around, he sits up, immediately regretting the earlier night's escapade as the pain hits him. Bruises lined his body, all the way from his neck to his thighs. His muscles ached, and he felt... sticky. Right, bodily fluids were still a thing. It had really been too long since he'd experienced being... alive again.

Giving in, the singer flops back down into his original position, trying to still his nerves. If he were alive, he probably wouldn't be able to move because of the pain, but his dead form took noticeably less damage. Mordekaiser truly had done a number on him, but he didn't regret it.

"Morning, dear." Morde purrs, bringing his arm up and running his fingers through Karthus' tangled silver hair. "Sleep well?"

"Like a corpse." He laughs, "And I think I'll continue sleeping."

"And why's that? Here I thought you were a man of ritual."

Karthus tries to move again, thus confirming his injuries. "I feel like you... beat the shit out of me last night."

Mordekaiser laughs, smacking the singer's back playfully. "I knew you'd regret it, but you didn't listen."

"I don't regret it." The singer says sternly, "I can handle a couple of bruises, you moron."

"A couple?" Mordekaiser turns over onto his side, pushing back the thick blanket to reveal Karthus' form. He runs his fingers over the bruises on Karthus' collar, then down to the large ones on his hips, probably from Morde grabbing him so roughly. "Looks like more than a couple to me."

"Fuck off. It's your fault for being such a brute." Karthus hisses as the guitarist's fingers prod at his newly formed bruises. His entire body was so tender, he couldn't help feeling a bit endangered.

"I can be gentle too, you know." He leans over the singer, placing his hand on an area free of bruises and pushing lightly, forcing Karthus onto his back. "I think you'll need a demonstration, since you obviously don't believe me."

"You're right, I don't."

Morde dips his head lower, his hair falling over his shoulders as he places a light kiss between the singer's hips, smiling. "Let me show you."

Karthus shifts uncomfortably as Mordekaiser spreads his thin legs, dragging his tongue across the singer's entrance teasingly. Carefully, he begins sucking on the tender flesh, paying extra attention to the singer's clit.

Writhing, he bites his lip instinctively. Ouch. He had forgotten that his lips were cursed with fresh wounds, and biting them had opened up one. "F-Fuck..." The metallic taste of blood on his tongue only made him more aroused, his clit throbbing in need.

Mordekaiser pulls away for a moment, licking his lips and smiling. "See?" He says teasingly, embracing the singer and pressing their lips together. He runs his tongue over Karthus' wound, fingers finding their way to his entrance to tease him some more.

"Nngh, hurry up..." Karthus hated being teased; Patience was not something he was particularly good at. All he wanted was to be fucked senseless, and he wanted it now.

"And where's the fun in that? I can't just give you everything you want." His fingertips brush through Karthus' sensitive folds, earning a breathy moan as he toys with his clit.

"F-Fuck you..." Karthus hisses, reaching down and taking hold of Morde's hand, pushing it closer. The hand resists, a low laugh coming from the guitarist. Karthus groans, rolling his eyes and bringing his own hand to his aid, beginning to roughly massage his clit.

"I know you can't get off on just that." Morde chuckles, "But it's a nice thought."

"And how would you know?"

Morde pushes two fingers inside swiftly, curling them upwards and hitting that perfect spot. Karthus immediately loses concentration, throwing his head back and moaning.

"I know you're a goddamn size queen." He withdraws his fingers, pushing them back in slowly and smiling as Karthus writhes. "Which is why I'm so fucking perfect for you."

Where Mordekaiser was getting this information from was beyond Karthus' knowledge, but he was right. Since pain could be easily ignored, Karthus enjoyed other sensations. He loved being treated like a toy, choked, gagged, and stuffed full of cock. He really was quite a whore, though no one would ever guess at first glance.

"H-How did you..." He knew that Morde wasn't quite that perceptive, and it wasn't like Karthus had any other partners. He hadn't told anyone about, well... anything, sexual related. How in the world did Mordekaiser know him so well?

"I'm actually surprised you didn't figure it out." Morde laughs, inserting a third finger, thrusting them in and out slowly. "I went through your little stash. Some interesting things in there."

"You w-what?!" His muscles tense, back arching. There was no way he'd have missed someone going through his things... He was very organized, and if anything was even remotely out of place, he knew. "How in the fuck..."

"Hm, no idea. You're normally so observant." Morde withdraws his fingers completely, taking no time to position himself between Karthus' thighs, cock fully erect. He presses inside slowly, holding the other's back as it arches, a low moan escaping his bruised throat. Since he had prepared Karthus beforehand, his cock slips in easily, and he begins moving his hips soon after. Morde pulls Karthus' legs above his hips, pressing deeper into his warmth. The singer couldn't help but to grin, being filled like this was just too damn good... Mordekaiser truly was quite perfect.

The two fuck for what seems like hours, finding climax several times before finally giving in to exhaustion. Mordekaiser rolls over onto his back, his huge chest rising and falling with each deep breath. As soon as they recover, Karthus moves over to lay beside Morde once more, draping his arm across the brute's waist and laying his head on his arm, just like before. They fit together rather nicely, both finding comfort in the other's presence.

"...You're something else, you know that?" Morde finally says, reaching up to run his finger's through Karthus' hair.

"Mm, what do you mean by that?" Karthus couldn't help but to find Morde's gentle touch to be endearing. It was a nice contrast to their sex, and a good way to wind down.

"I mean, like... You're not what you seem to be." Morde knew that his vocalist wasn't normal, in any sense of the word. Their odd differences were what brought them all together in the first place, and made Pentakill what it was today.

"Is that a bad thing?" Karthus muses, neither smiling or frowning at his comment.

"Nah, I like it." He leans over, planting a kiss on Karthus' forehead, smiling. "This was fun as hell, we should do it more often."

"You have a girlfriend." Karthus states, now frowning a little. As much as he would love to fuck Sona's boyfriend behind her back... He did in fact, have respect for her. And although he would never admit it, he was rather attracted to Morde.

"She doesn't have to know. I'll make sure to show her extra attention."

"Mm, I don't know..."

"C'mon, you can't say you didn't have fun. We're good for each other." Morde tilts Karthus' jaw up, bringing their lips together in a brief kiss. "Sona likes being alone some days, so I can come visit you and we can fuck like rabbits." He laughs a little, laying back down and smiling. "It'll be good for you, to clear your mind, stuff like that."

As much as Karthus did enjoy his toys, they were certainly no replacement for the real thing. In the past ten hours, he'd had more quality orgasms than he'd had in probably his entire existence. Save for one, which was given to him by a talented physical healer. Either way, it wouldn't hurt, right? Mordekaiser was good at keeping things like this to himself.

"Fine." Karthus finally says, exhaling. "This stays between us, obviously."

"Of course."


End file.
